B-TAU UNIFICATION AND NEUTRINO MASSES IN SU(5) EXTENSIONS OF THE MSSMWITH RADIATIVE ELECTROWEAK BREAKING

We make a complete analysis of the Yukawa coupling unification in SU(5 ) extensions of the MSSM in the framework of the radiative symmetry-br eaking scenario. Both logarithmic and finite threshold corrections of sparticles have been included in the determination of the gauge and Yu kawa couplings at M-Z. The effect of the heavy masses of each model in the renormalization group equations is also included. We find that in the minimal SU(5) model b-tau Yukawa unification can be achieved for too large a value of alpha(s). On the other hand, the Peccei-Quinn ver sion of the missing doubler model, with the effect of the right-handed neutrino also included, exhibits b-tau unification in excellent agree ment with all low energy experimental data. Unification of all Yukawa couplings is also discussed.